Mooring devices

ABSTRACT

The invention relates to a mooring device which includes a float intended for mooring below the surface of the sea, a sinker, a cable connecting the float to the sinker and means for paying out the cable. The device also includes control means for regulating the pay out of the cable in response to the ambient pressure at the float so as to tend to maintain the float at a predetermined depth below the surface during the mooring process, and in addition locking means operative to lock the paying out means when paying out ceases.

United States Patent [72] Inventor Hans Castelliz Halifax, Nova Seotia,Canada [21] Appl No. 654,892 [22] Filed July 20. 1967 [45] Patented Aug.10, 1971 [73] Assignee E M I Limited Hayes, England [32] Priority Aug.19, 1966 [33] Great Britain [31] 37,147/66 [54] MOORING DEVICES 10Claims, 5 Drawing Figs.

[52] US. Cl 9/8 [51] Int. Cl 1363b 21/52 [50] Field olSearch 9/8; 102/14[56] References Cited UNITED STATES PATENTS 1,011,152 12/1911Bruck...........i. 102/14 3,109,370 11/1963 Elmer et al. 102/14 PrimaryExaminer-Trygve M. Blix Attorney-William W. Downing, Jr.

ABSTRACT: The invention relates to a mooring device which includes afloat intended for mooring below the surface of the sea, a sinker, acable connecting the float to the sinker and means for paying out thecable. The device also includes control means for regulating the pay outof the cable in response to the ambient pressure at the float so as totend to maintain the float at a predetermined depth below the surfaceduring the mooring process, and in addition locking means operative tolock the paying out means when paying out ceases.

Patentd Aug. 10, 1971 2 Sheets-Sheet 1 Patented A 10, 1971 3,597,778

2 Sheets-Sheet 2 0 II o Has MOORING DEVICES This invention relates tomooring devices, and it relates in particular to mooring devices whichinclude a float intended for mooring below the surface of the sea.

For oceanographic, navigational and other purposes it may be desired tomoor a float so that it is submerged at a given depth below the surfaceof the sea, and various proposals have been made for achieving thisresult. For example where the depth of the sea is known, the float maybe attached to a sinker or anchor by a length of cable which is such asto maintain the float at the correct depth. However, in deep water,depth soundings cannot usually be obtained with sufficient accuracy toensure that the float is moored at the right depth. Another proposal isto sound the water depth withthe mooring cable itself, but in this casewhile the sounding is being taken, the ship may drift due to wind andcurrent so that the sinker while being lowered trails behind the ship,and the cable is measured too long. In addition the sounding operationcan only be performed in low sea states and requires time and skill.Another proposal is to attach a pilot line, with a weight at its end,below the sinker and as the pilot line descends with the sinker, thecable is paid-out from the sinker, leaving the'buoy on the surface. Whenthe weight on the end of the pilot line touches the bottom, the winch islocked and the float is pulled under by the sinker as it descends to thebottom. HOwever this proposal is unsuited for deep water, because thefloat may drift while on the surface and give rise to excessive payoutof the cable.

The object of the present invention is to provide an improved mooringdevice which includes a float which can be moored at a predetermineddepth with a relatively high degree of accuracy.

According to the present invention there is provided a mooring deviceincluding a float, a sinker, a cable connecting said float to saidsinker, means for paying out said cable between said float and saidsinker, means for regulating the payout of the cable by said paying outmeans in response to the ambient pressure at said float so as to tend tomaintain said float at a predetermined depth below the surface duringthe mooring process, and locking means for locking said paying outmeans,-means for sensing when pay out ceases, and operating meansresponsive to said sensing means for operating said locking means toinhibit further payout of the cable.

In order that the present invention may be clearly understood andreadily carried into effect it will now be described with reference tothe accompanying drawings in which:

FIG. 1 illustrates diagrammatically one example of a mooring deviceaccording to the present invention,

FIG. 2 is a detailed view on a larger scale of part of the deviceillustrated in FIG. 1,

FIG. 3 illustrates a locking device incorporated in the deviceillustrated in FIG. 1, which is however not visible in that FIG.,

FIG. 4 illustrates a modification of the arrangement shown in FIG. 1,and

FIG. 5 illustrates part ofa mooring device incorporating themodification illustrated in FIG. 4.

Referring to the drawings, the device illustrated in-FIG. 1 comprises afloat 1 which is called a subsurface float because it is intended to bemoored below the surface of the sea. A frame 2 suspended from theunderside of the float 1 carries a cable drum 3, the drum 3 being freelyrotatable in bearings one of which is denoted by the reference 4. As canbe seen more clearly in FIG. 2, the drum 3 has brake shoes 5 which canbe applied by levers 6 pivoted at 7. The top ends of the levers 6 arebiased by a tension spring 8 which tends to maintain the shoes 5 appliedto the drum so as to brake the drum. Bellows 9 are connected between thelevers 6 and the frame 2 in such a way that, when an increase in ambientpressure causes the bellows to contract, the action of the spring 7 iscountered and the pressure of the shoes 5 on the drum 3 is reduced.Components -2 to 9 are referred to as the winch. A cable 10 in the formofa steel wire is wound on the drum 3, the free end of the cable beingattached to a sinker 11, the cable passing from the frame 2 through ahawse pipe 12.

The winch is provided with a locking device adapted to lock the drum 3so that no more cable can be paid-out after the sinker 11 has reachedthe ocean bottom. This locking device comprises a series of notches 13(FIG. 3) provided at intervals around the periphery of the drum 3. Alocking plunger 14, which can slide in guides 15, is biased by a spring16 so that the plunger tends to move towards the drum and engage in oneofthe notches 13 so locking the drum. However a latch 17 is fitted whichcan hold the plunger withdrawn from the notches, allowing the drum torotate. A cam 18 is mounted on the winch shaft so as to rotate with thewinch, and this operates the piston 19 of a water pump 20, which isarranged to pump water into a dashpot cylinder 21, which has a meteringhole 22 The dashpot has a piston 23 attached to a rod 24, and when thepiston is raised by water in the cylinder 21, the rod 24 can enter ahole 25 in the locking plunger 14 and thereby lock the plunger and atthe same time release the latch 17.

Before the mooring device is installed, the cable 10 is fully wound onthe drum and the locking plunger 14 is cocked by withdrawing it from thedrum 3 and latching it by means of the latch 17. At this time, thepiston 23 of the dashpot 21 is at the lower end of its travel and therod 24 does not project into the hole 25. The mooring device, can thenbe lowered into the sea at the selected area and allowed to sink underthe influence of the sinker. When the device reaches a predetermineddepth, called the setting depth" the compression of the bellows 9releases the pressure of the brake shoes 5 sufficiently to allow thedrum to turn under the pull of the sinker 1 1 which separates from thefloat l as the cable is paid-out. 1f the float depth tends to changefrom the setting depth, the brake is either tightened to lower the floatif ascending or loosened to allow the float to rise, ifdescending. Thusthe brake automatically tends to maintain the float at the setting depthat all times until the sinker reaches the ocean bottom.

As long as the sinker is descending relative to the float, the winchdrum 3 rotates and the pump 20 is operated by the cam 18. The first fewstrokes of the pump 20 fill the dashpot cylinder 21 and drive the piston23 to its upstroke position, pushing the rod 24 through the hole 25 andreleasing the latch 17. The locking plunger 14 then moves horizontally ashort distance towards the drum 3 by the action of the spring 16sufficient to prevent the latch 17 from becoming reengaged but notsufficient to cause the plunger 14 to enter any notch 13. Furthermovement of the plunger is prevented by the rod 24. When the sinker 11reaches the ocean bottom, the pump 20 ceases to operate and the piston23 slowly returns towards its down stroke position under the action ofspring 26, the rate of return being determined by the rate of whichwater can flow through the metering hole 22 in the cylinder 21. Thedashpot is designed so that the time taken for the piston 23 to reachits down stroke position is about 2 minutes. When the piston reaches itsdown stroke position the rod 24 is withdrawn from the hole 25 in thelocking plunger 14 and the plunger is now forced into its lockingposition by the spring 16. The time delay provided by the dashpotmechanism is required because the winch drum may stop rotating for shortperiods of time during the payout of the cable, and these shortstoppages could otherwise cause premature locking of the drum. Itwill beappreciated that if the rotation of the drum is restarted prior to theend of the two minute period, the pump 20 quickly returns the dashpotpiston 23 to its up stroke position and prevents the release of theplunger 14.

The device described has the advantage that the float is kept below thesurface of the sea from the beginning of the cable payout and so thefloat is not exposed to surface currents and wind. The possibility of ahorizontal offset between it and the sinker is therefore reduced andwhen the float is moored, the cable is taut and vertical. Moreoverknowledge of the water depth is not required prior to launching as longas it is less than the cable length, and weather conditions have nodetrimental effect on the mooring operation.

During the operation, when the ambient pressure at the float correspondsto the setting depth, the resulting force on the brake levers 6 is suchthat the drum is allowed to rotate under a cable pull P, and P is equalto the upward force F provided by the buoyancy of the float 1 less theweight in water of the winch assembly, there being equilibrium betweenthe forces P and F. The weight W of the sinker under water is greaterthan the force P and the sinker descends with such a speed that the dragagainst it compensates for the excess weight. In any position of thesubsurface float lower than the equilibrium depth the ambient pressuretends further to release the brake shoes which results in a cable pull Pless than the upward thrust F. This restores the float I to theequilibrium position. In positions of the float 1 higher than theequilibrium position the converse occurs. Therefore the system is aservosystem and the equilibrium state is a stable state.

The torque which is applied to the winch drum 3 by the cable is T=PRwhere R is the effective spool radius. As the cable is paid out, R andtherefore the torque decreases and rotation tends to cease. Consequentlythe system is pulled to a greater depth until the brake is releasedsufficiently to let the drum rotate under the reduced torque. Thus thefloat 1 tends to descend to a depth somewhat below the setting depth asthe cable unwinds. On the other hand the buoyancy F and therefore alsothe cable tension P increase as the cable weight is taken off the drum3. Under this influence, the torque PR tend to increase and the float lrises. These two influences, namely change of weight and change of spoolradius, counteract each other in their effect and may be made tocompensate one another by a suitable selection of the drum dimensions.Incomplete compensation results in a certain change of equilibrium depthduring cable payout, but this can be made negligible.

In the modification which is illustrated in FIG. 4 the brake shoes arereplaced by a band 30. Moreover the bellows 9 are replaced by a piston31 which moves in a cylinder 32. The piston 31 is biased by a tensionspring 33 against the pressure of the sea on the upper surface of thepiston. The piston is connected to a lever 34 fulcrumed at 35 andcoupled to the band so as to adjust the tension thereof. The directionof rotation of the drum 3 during unwinding is denoted by the arrow 36and it can be seen that the lever operates on the taut end of the band30, rather than on the slack end. This renders the brake torquepractically independent of the coefficient of friction, which isdesirable because the coefficient of friction may change considerablyunder water, as a result of organic material being caught in themechanism. The setting depth of the float 1 may be adjusted beforelaunching by changing the tension of the spring 33. Such adjustment canalternatively be achieved by connecting the underside of the piston 31(as seen in the drawing) to an air container and by adjusting the airpressure.

FIG. 5 illustrates one example of a mooring device incorporating thebrake of FIG. 4. The references used in FIG. 5 are the same as those ofFIGS. 1 and 4 where applicable. The reference 40 denotes a container forcompressed air, coupled to the cylinder 32 at the underside of thepiston 31 by means ofa pipe 41. By adjusting the air pressure incylinder 32 before launching, the setting depth can be adjusted. Thepiston in the cylinder 32 is connected to the lever 34 by a piston rod42 which is biased by the spring 33.

The launching of a mooring device in accordance with the invention maybe facilitated by arranging that the float portion and the sinker arefirmly locked together by connecting means which is released once thedevice is in the sea. The operation of releasing the connecting meansmay be initiated by a pres sure sensitive device or alternatively by thechemical or physical action of the sea water.

What I claim is: l. A mooring device including a float, a sinker, acable connecting said float to said sinker, means for paying out saidcable between said float and said sinker, means for regulating payout ofcable by said paying out means in response to the ambient pressure atsaid float so as to tend to maintain said float at a predetermined depthbelow the surface during the mooring process, locking means for lockingsaid paying out means, sensing means for sensing when said payoutceases, and operating means responsive to said sensing means foroperating said locking means to inhibit further payout of the cable.

2. A device according to claini l in which said paying out meanscomprises a rotatable drum carried by said float and on which said cableis initially wound, and said sensing means includes means to sense whensaid drum ceases to rotate.

3. A device according to claim 1 in which said operating means includestiming means to retard operation of said locking means for apredetermined time after said sensing means has sensed that payout ofthe cable has ceased.

4. A mooring device including a float, a sinker, a cable con nectingsaid float to said sinker, means including a rotatable drum carried bysaid float and on which said cable is initially wound for paying outsaid cable between said float and said sinker, means for regulatingpayout of cable by said paying out means in response to the ambientpressure at said float so as to tend to maintain said float at apredetermined depth below the surface during the mooring process,locking means for locking said paying out means, sensing means includinga hydraulic pump operated by rotation of said drum for sensing when saidpayout ceases, and operating means responsive to the cessation ofoperation of said hydraulic pump for operating said locking means toinhibit further pay out of the cable.

5. A mooring device including a float, a sinker, a cable connecting saidfloat to said sinker, means including a rotatable drum carried by saidfloat and on which said cable is initially wound for paying out saidcable between said float and said sinker, a brake acting on said drum,spring means including a pneumatic reservoir containing a compressiblefluid for applying said brake, and ambient pressure dependent releasemeans acting in opposition to said spring means to release said brakemeans thereby to regulate payout of cable so as to tend to maintain saidfloat at a predetermined depth below the surface during the mooringprocess, locking means for locking said paying out means, sensing meansfor sensing when said payout ceases, and operating means responsive tosaid sensing means for operating said locking means to inhibit furtherpayout of the cable.

6. A device according to claim 4 in which said operating means includestiming means to retard operation of said locking means for apredetermined time after operation of the said pump ceases, said timingmeans including a dashpot into which fluid is forced by the operation ofsaid pump, said dashpot being arranged to allow operation of the lockingmeans when the fluid in the dashpot falls below a predetermined level.

7. A device according to claim 1 in which said regulating means includesa brake acting on said drum, spring means for applying said brake, andpressure dependent release means acting in opposition to said springmeans.

8. A device according to claim 5 including means for adjusting thepressure of said compressible fluid in said reservoir to determine thedepth of mooring of said float beneath the surface.

9. A device according to claim 5 in which said pressure dependent meanscomprises a piston forming one wall of said reservoir, and exposed onits outer side to ambient pressure.

10. A device according to claim 5 in which said brake is a friction bandbrake controlled at the taut end thereof by said spring means.

1. A mooring device including a float, a sinker, a cable connecting saidfloat to said sinker, means for paying out said cable between said floatand said sinker, means for regulating payout of cable by said paying outmeans in response to the ambient pressure at said float so as to tend tomaintain said float at a predetermined depth below the surface duringthe mooring process, locking means for locking said paying out means,sensing means for sensing when said payout ceases, and operating meansresponsive to said sensing means for operating said locking means toinhibit further payout of the cable.
 2. A device according to claim 1 inwhich said paying out means comprises a rotatable drum carried by saidfloat and on which said cable is initially wound, and said sensing meansincludes means to sense when said drum ceases to rotate.
 3. A deviceaccording to claim 1 in which said operating means includes timing meansto retard operation of said locking means for a predetermined time aftersaid sensing means has sensed that payout of the cable has ceased.
 4. Amooring device including a float, a sinker, a cable connecting saidfloat to said sinker, means including a rotatable drum carried by saidfloat and on which said cable is initially wound for paying out saidcable between said float and said sinker, means for regulating payout ofcable by said paying out means in response to the ambient pressure atsaid float so as to tend to maintain said float at a predetermined depthbelow the surface during the mooring process, locking means for lockingsaid paying out means, sensing means including a hydraulic pump operatedby rotation of said drum for sensing when said payout ceases, andoperating means responsive to the cessation of operation of saidhydraulic pump for operating said locking means to inhibit further payout of the cable.
 5. A mooring device including a float, a sinker, acable connecting said float to said sinker, means including a rotatabledrum carried by said float and on which said cable is initially woundfor paying out said cable between said float and said sinker, a brakeacting on said drum, spring means including a pneumatic reservoircontaining a compressible fluid for applying said brake, and ambientpressure dependent release means acting in opposition to said springmeans to release said brake means thereby to regulate payout of cable soas To tend to maintain said float at a predetermined depth below thesurface during the mooring process, locking means for locking saidpaying out means, sensing means for sensing when said payout ceases, andoperating means responsive to said sensing means for operating saidlocking means to inhibit further payout of the cable.
 6. A deviceaccording to claim 4 in which said operating means includes timing meansto retard operation of said locking means for a predetermined time afteroperation of the said pump ceases, said timing means including a dashpotinto which fluid is forced by the operation of said pump, said dashpotbeing arranged to allow operation of the locking means when the fluid inthe dashpot falls below a predetermined level.
 7. A device according toclaim 1 in which said regulating means includes a brake acting on saiddrum, spring means for applying said brake, and pressure dependentrelease means acting in opposition to said spring means.
 8. A deviceaccording to claim 5 including means for adjusting the pressure of saidcompressible fluid in said reservoir to determine the depth of mooringof said float beneath the surface.
 9. A device according to claim 5 inwhich said pressure dependent means comprises a piston forming one wallof said reservoir, and exposed on its outer side to ambient pressure.10. A device according to claim 5 in which said brake is a friction bandbrake controlled at the taut end thereof by said spring means.